How to configure AcousticBF library for PCM mode on STM32L476RG?

[PIvan.9]

I'm trying to implement AcousticBF library functions and what I've noticed is that, when I configure it like this for PCM mode, 2 microphones:

void Audio_Libraries_Init(void)
{
  volatile uint32_t error_value = 0;
  /* Enable CRC peripheral to unlock the library */
  __CRC_CLK_ENABLE();
  /*Setup Beamforming static parameters*/
  error_value = 0;
  libBeamforming_Handler_Instance.algorithm_type_init=ACOUSTIC_BF_TYPE_CARDIOID_BASIC;
  libBeamforming_Handler_Instance.ref_mic_enable=ACOUSTIC_BF_REF_ENABLE;
  libBeamforming_Handler_Instance.ptr_out_channels=2;
  libBeamforming_Handler_Instance.data_format=ACOUSTIC_BF_DATA_FORMAT_PCM;
  libBeamforming_Handler_Instance.sampling_frequency=16;
  libBeamforming_Handler_Instance.ptr_M1_channels=1;
  libBeamforming_Handler_Instance.ptr_M2_channels=1;
  libBeamforming_Handler_Instance.delay_enable = 0;
  (void)AcousticBF_getMemorySize(&libBeamforming_Handler_Instance);
  libBeamforming_Handler_Instance.pInternalMemory =(uint32_t *)malloc(libBeamforming_Handler_Instance.internal_memory_size);
  error_value = AcousticBF_Init(&libBeamforming_Handler_Instance);
 
  /*Error Management*/
  if(error_value != 0U)
  {
   Error_Handler();
  }
 
  /*Malloc Failure*/
  if(libBeamforming_Handler_Instance.pInternalMemory == NULL)
  {
    Error_Handler();
  }
 
  /*Setup Beamforming dynamic parameters*/
  lib_Beamforming_Config_Instance.algorithm_type = ACOUSTIC_BF_TYPE_CARDIOID_BASIC;
  lib_Beamforming_Config_Instance.M2_gain = 0.0f;
  lib_Beamforming_Config_Instance.mic_distance = 212;
  lib_Beamforming_Config_Instance.volume = 24;
  error_value = AcousticBF_setConfig(&libBeamforming_Handler_Instance, &lib_Beamforming_Config_Instance);
 
  /*Error Management*/
  if(error_value != 0U)
  {
    Error_Handler();
  }
}

then, AcousticBF_FirstStep function returns 0, so I can't implement AcousticBF_SecondStep() function further:

void AudioProcess(void)
{
    if(AcousticBF_FirstStep(&((uint8_t *)(PCM_Buffer))[0],&((uint8_t *)(PCM_Buffer))[1], (int16_t *)Out_Buffer, &libBeamforming_Handler_Instance) == 1U)
    {
      SW_Task1_Start();
    }
 
  /*for L4 PDM to PCM conversion is performed in hardware by DFSDM peripheral*/
  Send_Audio_to_USB((int16_t *)Out_Buffer, (AUDIO_IN_SAMPLING_FREQUENCY/1000)*AUDIO_IN_CHANNELS);
}

Is there smth I missed? Or did I configure smth wrong?